Preparation of titanium pigments



Patented Jan. 3, 1933 I UNITED STATES PATENT OFFICE JOSEPH BLUMENFELD,OF PARIS, FRANCE, AND MAX MAYER, OF KARLSBAD, CZEGHO- SLOVAKIA,ASSIGNORS, BY MESNE ASSIGNMENTS, TO KREBS PIGMENT AND COLOR CORPORATION,OF NEWARK, NEW JERSEY, A CORPORATION OF DELAWARE PREPARATION OI TITANIUMPIGMENTS No Drawing. Continuation of applications filed January 13-,1925, Serial Nos. 2,233 and 2,284, and in Germany August 11, 1924.Division of application fl1ed May 15, 1930, Serial 1T0. 452,810. Thisapplication filed May 15, 1930, Serial No. 452,811.

This invention relates to improvements in the preparation or manufactureof titanium pigments and the improved products resulting from suchimproved process.

5 Titanium pigments have been used extensively as substitutes for otherpigments and have shown a general superiority over such pigments,especially when compared to other White pigments. Theyare,however,inclined to become powdery or to chalk oil and thischaracteristic makes them objectionable for use wherethey will beexposed to the weather.

This application is a division of our application Serial Number 452,810filed May 15,

1930 and a continuationof our copending applications Serial Numbers2,233 and 2,234, filed January 13, 1925.

It is an object of the present invention to provide a process forpreparing a titanium pigment of improved characteristics and one whichmay be safely used where it will be exposed to the weather. It isanother object to provide a method for preparing a pigment havinggreater durability and one which will not be subject to the abovedefect. It is also an object of the invention to improve the quality ofthe pigment by controlling the conditions under which it is sintered.Another object of the invention is to produce a new.

pigment of improved characteristics. Other objects will become apparent.

The invention, broadly stated, comprises adding to precipitated titanicacid, substances which will improve the characteristics of the pigmentresulting from the calcining operation. It also includes the addition ofsubstances adapted to fill and remain in the interstices or pores of thetitanium pigments as Well as the addition of materials adapted to assistin the sintering action but which materials may be subsequently washedfrom the pigment.

In view of the pigmentary qualities required in the finished product,the materials added to fill the interstices or pores should have theessential characteristics of pigments or at least they should notdetrimentally affeet the pigmentary qualities'of the product.

of the interstices or pores of the titanium oxide by the deposition ofthe finely divided particles resulting from the coagulation orprecipitation, and the retention of these particles during the dryingand calcinin steps, result in a product having increa durability anddecreased oil absorption.

The oxides and hydroxides of the tetravalent rare earths of thetitanium-thorium family, which family also includes zirconium andcerium, have suitable characteristics for use in this connection and maybe applied to the titanium oxide by precipitation or coagulation fromsolutions in which the titanium oxide is suspended.

We have also found that an improvement in the sintering of the abovecomposite pigment or of the titanium oxide alone, may be accomplished'byefiecting the sintering in an acid atmosphere produced by free acids orby the heating of salts of an acid character. It is preferable to usefor this purpose salts 'whose residues may be removed by washing thecalcined product. Alkali salts are examples of substances suitable forthis purpose.

In carrying out our improved rocess, the titanium oxide 'may be mixedwith the rare earth compound, preferably the hydroxide or oxide incolloidal solution, and the rate earth oxide or hydroxide ma bedeposited upon and within the pores o the particles of titanium oxideeither by precipitation or coagulation. The composite precipitateresulting from the filling of the pores of the titanium oxide with therare earth oxide or hydroxide may then be calcined at 8001000 C. to giveit the desired igment properties.

Titanium oxide adapta le to be pore filled as described herein may beobtained con- 5 veniently from the main titanium product of the processdescribed in United States Patent 1,504,672, but other tetravalentoxides of titanium obtained by precipitation and having any degree ofhydration are also suitable and can be used in the present case.Further, these oxides or hydroxides may or may not be dried and/orcalcined before they are put in suspension in the solution. In caseshere the oxide has been calcined it is,

of course, referable to bring it first to a fairly fine state ofdivision.

In order to describe our invention more clearly, the following specificexamples are given. It is not intended, however, to restrict theinvention to the particular conditions and proportions recited, since itis apparent that these examples are only illustrative and manymodifications may be made to obtain the desired improvement.

Example I About 7 to 10 parts by weight of finely ground, preferablycalcined,'titanium oxide 15 suspended in 100 parts by weight of a so- 80lution of titanium or titanyl sulphate containing about 200 grams oftitanium oxide per litre. This sulphate solution may be obtained by thecustomary procedure of treating ilmenite with sulphuric acid. Themixture is heated to hydrolyticallyprecipitate titanium oxidefrom thesulphate solution upon the suspended titanium oxide. The

heating may be done under atmospheric or increased pressure and a refluxcooler may 40 be used if it is desired to prevent evaporation.

The pore-filled titanium oxide is separated from the solution, forinstance, by filtering, and may be washed to free it from acid, and

calcined at about 800-1000 C.

Example [I About 10 parts by weight of calcined titanium oxide arefinely ground and mixed with 7 parts by weight of a colloidal thoriumsolution containing about 300 grams of thorium oxide per litre ofsolution. The water of the mixture is evaporated and calcination iseffec'ted at red heat. The calcined product may be cooled and ground ina wet or dry con dition.

The calcining of the titanium dioxide before depositing the thoriumoxide gives the particles a definite structure upon which the 00 porefilling material may be deposited. It is apparent that a similarimprovement may be accomplished by adding the finely ground calcinedtitanium oxide to a colloidal solution of titanium oxide and coagulatingthe colloidal titanium dioxide.

If preferred, the titanium or thorium oxide may be coagulated by heatingand the water may be separated from the suspended material by decantingand/or filtering, after which the composite solids may be calcined andground.

An improved result may also be obtained by using moist precipitatedtitanium dioxide, containing about 50% water, in place of the calcinedmaterial referred to in the above illustrations.

E sample Ill The pore-filled titanium oxide, referred to in the aboveexamples, may be calcined in the presence of a salt. For example, asmall quantity of colloidal titanium or thorium oxide may be mixed withtitanium oxide and this mixture may be dispersed in sodium sulphatesolution. The sodium sulphate will coagulate the colloidal titanium orthorium oxide and the water may then be evaporated or otherwiseseparated from the mixture of solids which may then be calcined byheating to about 800-1000 C. After the calcining the sodium sulphateremaining upon the pigment may be separated by washing the calcinedmixture. If desired, other salts, such as potassium carbonate, may besubstituted for the sodium sulphate.

Example I V An improved product will also result from sintering thetitanium oxide with a salt, without the addition of a pore-fillingmaterial. As an illustration, 10 parts by weight of titanium oxide in amoist or dry condition are intimately mixed with two parts by weight ofpotassium bisulphate and the mixture may be calcined at a temperature of800 to 1000 C. The sulphuric and sulphurous acid given off during theheating may be collected and utilized. After heating, the potassiumsulphate is extracted from the calcined materials by washing with waterand any remaining acid may be removed by treating the moist or dryproduct with an oxide of a metal capable of reacting with the sulphateto form a residue having pigmentary qualities, for example, zinc oxideor magnesium oxide. A considerably smaller quantity of potassiumbisulphate, for example as little as 2%dof the weight of titanium oxide,may

e use 1 Example V As another example of the heating of titanium oxidewith an alkali salt, 10 parts by weight of moist titanium hydroxide,obtained from a neutral or basic titanium sulphate solution, areintimately mixed with about 0.5 parts by weight of potassium carbonate,and the mixture is heated for a suitable time, for example, two hours,at a temperature of about 8001000 C. The calcined material is washedfirst with water to remove the potassium sulphate and then with mineralacid until completely neutral and is then dried. A considerably smallerquantity of potassium carbonate maybe used, for example, verysatisfactory results are obtained y using potassium carbonate in theproportion of 0.5% of the titanium oxide. If the oxide, referred to inthe above examples, is obtained by precipitating titanium sulphatesolution, it will contain sufiicient sulphuric acid to convert thealkali carbonate to a sulphate. A similar. result may be obtained byadding an alkali hydroxide.

The improvement in whiteness of the pigment resulting from the calciningin the presence of an alkali salt does not seem to be dependent upon thepresence of the sulphate radical, since similar improvement may beaccomplished by heating in the presence of other alkali salts. Imrovements in results may be accomplished y adding the alkali salt inproportions up to about 2% of sodium salt, but the addition of a-greateramount these elements does not greatly improve the whiteness of theproduct. The quantity of water soluble salt present during the calciningmay be regulated y controlling the concentration of the solution fromwhich the solids are separated or by Washing the separated solids so as.to remove a portion only of the water soluble salt. It is a parent thatvarious modifications and com inations of theabove illustration may beused and that the quantities may be varied and it is not intended torestrict the invention to the particular embodiment described. In the apended claims the term titanium-thorium amily is used to include cerium.

The sintered product produced accordin to the above processes, ormodifications 0 these rocesses, maybe ground wet or dry and mixed withthe usual diluting agents and fillers, such as barium sulphate, zincoxide and others, to roduce a durable primary material for paints andother oovermg materials and one which ,may be'applied where it is to beexposed .to the weather.

We claim: e 1. In the preparation of a titanium pigment, the stepscomprising mixing moist titanium oxide with less than 2% of alkalicarbonate in the presence of sulphate ions, calcining the mixture andwashing the calcined materials to remove the water soluble residue.

2. In a process for producing a white titanium oxide pigment, the stepof calcining at a temperature upward of about 800 C, a mixturecomprising a precipitated titanium oxygen compound and an alkali metalcompound.

3. In a process for producing a white titanium oxide pigment, the stepof calcining together with zirconium and at a temperature upward ofabout 800 C, a mixture comprising a precipitated titanium oxygencompound and a sodium compound. 4. In a process for producing a whitetitanium oxide pigment, the step of calcining at a temperature upward ofabout 800 C, a mix ture comprising a precipitated titanium oxygencompound and a potassium compound.

5. In a rocess for preparing a titanium 7 pigment, t e steps ofincorporating into a precipitated titanium oxygen compound apredetermined amount of an alkali-metal compound andcalcining saidmixture at a temperature upward of about 800 C.

6. In a process for producing a white titanium oxide pigment, the stepsof incorporating into a precipitated titanium oxy en compound apredetermined amount 0% a potassium compound and calcining the mixtureat a temperature upward of about 800 C.

7. In a process for producing a white titanium oxide pigment, the stepsof incorporating into a precipitated titanium oxygen compound apredetermined amout of a sodium compound and calcining the mixture at atemperature upward of about 800 C.

8. In a process for producinga white titanium oxide pigment, the stepsof incorporating into a precipitated titanium oxygen compound from about0.5 to 5% of potassium carbonate and calcinin the mixture at atemperature upward of a out 800 C.

" 10. In a process for preparing a titanium pigment, the steps ofincorporating into a precipitated titanium oxygen compound apredetermined amount of an alkali-metal compound andv calcining saidmixture at a temperature of about 800 to 1000 C.

- 11. In a process for producing a white titanium oxide pigment, thesteps of inoorpo-- rating into a precipitated titanium oxygen compoundfrom about 0.5 to 20% of a potassium compound and calcining the mixtureat a temperature of about 800 to 1000 C.

12. In a process for producing a white'titanium oxide pigment, the stepof incorporating into a precipitated titanium oxygen compound from about0.5 to 5% of potassium carbonate and calcining the mixture at a tem-.perature of about 800 to 1000 C.

13. In a process for preparing a white pig 'ment, the steps compnslngadding an alkalimetal compound to a'titanium oxygen compound obtained bthe hydrolysis of a titanium sulphate so ution and containing thesulphate radical, and calcining the mixture at a temperature upward ofabout 800 C.

14. In a process for preparing a white pig- April, 1930.

MAX MAYER.

